module: Wait for RCU synchronizing before releasing a module

Wait for RCU synchronizing on failure path of module loading
before releasing struct module, because the memory of mod->list
can still be accessed by list walkers (e.g. kallsyms).

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/module.c b/kernel/module.c
index 88cec1ddb1e3..331b03f6b411 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3326,6 +3326,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
         /* Unlink carefully: kallsyms could be walking list. */
         list_del_rcu(&mod->list);
         wake_up_all(&module_wq);
+        /* Wait for RCU synchronizing before releasing mod->list. */
+        synchronize_rcu();
         mutex_unlock(&module_mutex);
  free_module:
         module_deallocate(mod, info);